1. Field of the Invention
The present invention relates to a power amplifier circuit, and more particularly, to a power amplifier circuit capable of improving cross isolation between a high frequency band power coupler and a low frequency band power coupler, by directly transmitting power to the high frequency band power coupler and the low frequency band power coupler from a power amplifier, and forming a predetermined inductance circuit or an LC resonance circuit in a line transmitting the power to the high frequency band power coupler.
2. Description of the Related Art
Recently, an electronic device adopting a wireless communication circuit has been widely used due to the easy use and mobility thereof, and the advantageous installment and maintenance thereof.
The electronic device adopting this wireless communication circuit is representatively a mobile terminal, a personal digital assistance (PDA), or the like.
In the electronic device adopting this wireless communication circuit, a transceiver transmitting and receiving a signal containing information is employed.
In the transceiver, a power amplifier circuit amplifying the power of a signal which necessarily needs to be transmitted or a received signal is used.
The output signal of the power amplifier circuit is subjected to power coupling and impedance matching and transmitted to an antenna and a receiving circuit. As shown in FIG. 1, this power amplifier circuit may include a power amplifier 11 and a power coupler 12. Meanwhile, the power amplifier 11 and the power coupler 12 are integrated in a single substrate. In this case, the power amplifier 11 may be formed by a complementary metal oxide semiconductor (CMOS) process and the power coupler 12 may be formed by an integrated passive device (IPD) process.
In this structure, power supplied to the power amplifier 11 is transmitted to a high frequency band power coupler 12a and a low frequency band power coupler 12b of the power coupler 12 through an external power supply pad 13 and an external bonding wire 14. However, since the power amplifier 11 has a limitation in performing cross isolation capable of restricting the output in a high frequency band when the power amplifier 11 operates in a low frequency band, it may not satisfy with the demands of a user requiring the cross isolation of at least −20 dBm or less.